IP Multimedia Subsystem (IMS) is a generic architecture for offering multimedia and voice over IP services. Advantageously, IMS is access independent as it supports multiple access types including Global System for Mobile (GSM), Wideband Code Division Multiple Access (W-CDMA), Code Division Multiple Access (CDMA), Wireless Local Area Network (WLAN), Wireline and other packet data applications. Consequently IMS may facilitate the ubiquitous availability of interne technologies such as web browsing, e-mail, messaging and video conferencing while enabling service providers to introduce new services.